Development of analytical sensors for the identification and quantification of metals in environmental samples

Expanded Title:

South Africa has a wealth of mineral resources, the mining activities for which have in some cases brought about environmental problems, both historic and current. Many of the big rivers in the country descend from the Great Escarpment of the interior to the coastal lowlands, contributing to a high rate of runoff and associated soil erosion. The use of fast, reliable and continuous monitoring techniques for water quality analysis has become essential. This project assessed the aquatic environment around platinum group metal mining, determining to what extent the aquatic environment has been polluted by these mining activities, and determined whether the current analytical tools and techniques used to analyse metals are adequate.
Environmental water samples displayed low metal concentrations. Seasonal influences affected the diversity of taxa for the biota samples collected and the metal concentrations within these samples. High Ni, Pb and Zn concentrations were recorded and it is possible that these metals are released from the sediment-water interface. The concentrations in the biota and algae were low, indicating that mining activities had a low impact at the sampling sites. The August biota samples showed higher concentrations of Al, Fe, Ni, Zn and Pt than in November. This may be due to higher water flow during November 2010, since sampling was done during the rainy season.
The main focus was the development of an electrochemical sensor for the identification and quantification of metals in environmental samples. The results showed that modifying the surface of a glassy carbon electrode with a bismuth film assisted in the stripping analysis of the M(HDMG)2 complexes, with M as the PGM (Pd, Pt and Rh) and dimethylglyoxime (DMG) as the chelating agent. The results obtained for the evaluation of the sensor showed varying results. The pH, DMG concentration, deposition potential, deposition time and PGM concentration were optimised. The effect of interfering ions was investigated and Ni(II) and Co(II) were the main interferences. The limit of detection (LOD) was found to be 0.12  0.06 µg/L for Pd, 0.04  0.007 µg/L for Pt and 0.23  0.04 µg/L for Rh. The ranges to which the sensor can be applied were 0.1 – 3.5 µg/L for Pd, 0.5 – 4.0 µg/L for Pt and 0.1 – 4.0 µg/L for Rh. The sensor was successfully applied in the determination of Pd, Pt and Rh in freshwater and sediment samples.

Date Published:

09/08/2012

Document Type:

Research Report

Document Subjects:

Mine water - Mine water treatment

Document Keywords:

Water Quality

Document Format:

Report

Document File Type:

pdf

Research Report Type:

Standard

WRC Report No:

2013/1/12

ISBN No:

978-1-4312-0279-9

Authors:

Somerset V; van der Horst C; Silwana B; Walters C

Project No:

K5/2013

Originator:

WRC

Organizations:

CSIR Natural Resources and the Environment Stellenbosch; Department of Chemistry University of the Western Cape; Department of Applied Sciences, Cape Peninsula University of Technology, Bellville